1. Field Of The Invention
The present invention relates digital signal processing and to apparatus and methods for identifying speech and tone energy on a signal line. More particularly, the present invention relates to apparatus and methods for identifying and discriminating between tones, such as DTMF tones, dial tones, busy signals and other tones used in telephone systems, and speech energy on a signal line.
2. The Prior Art
While numerous theoretical models of speech may be found in the literature, real-time identification of electrical energy as comprising human speech presents a challenge. Real-world, real-time applications of speech-recognition often have low tolerance for false positive and false negative speech-present decisions. An example of such an application is in PBX and other telephone applications, where human speech and call-progression tones are expected to be encountered on the same line within adjacent time windows. There is a need in such systems to accurately identify and distinguish between both call-progression tones and speech components of electrical energy present on a signal line for controlling the operation of the PBX or other control system. The use of false positive and false negative speech-present or tone-present determinations to control the operation of such a system can render a product commercially undesirable. In the ideal case, apparatus capable of reporting the presence of speech or call-progression tones on a signal line would have an accuracy of 100%, however, this goal has not been achievable using prior art technology.